How can I create a bump line across an object using textures?
You can do the following...


Add a Bump Node
Add invert node to your bump map texture.
Plug it into the height input on the Bump node.
Plug the bump node into the Normals channel of your shaders.
Adjust the strength value on the Bump node, to match your need.


Note bump is exaggerated for demostration purposes.



Here is the blend file.